1. Field of the Invention
The invention relates to a thin film magnetic head having at least an inductive magnetic transducer for writing, a method of manufacturing the same and a method of forming a magnetic layer pattern in other technical fields.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in a surface recording density of a hard disk drive. A composite thin film magnetic head, which has a stacked structure comprising a recording head having an inductive magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinafter referred to as MR) element for reading, is widely used as the thin film magnetic heads.
To increase a recording density of the performance of the recording head, it is necessary to increase a track density on a magnetic recording medium. For this purpose, it is necessary to realize a recording head having a narrow track structure in which a top pole and a bottom pole, which are formed on and under a write gap therebetween, respectively, have a narrow width of from a few microns to the submicron order on an air bearing surface, and semiconductor fabrication technology is used in order to achieve the recording head having the above-mentioned structure.
The description is now given with reference to FIGS. 39 to 44 with regard to a method of manufacturing a composite thin film magnetic head as an example of a method of manufacturing a thin film magnetic head of the related art.
In the manufacturing method, first of all, as shown in FIG. 39, an insulating layer 102 made of, for example, aluminum oxide (Al2O3, hereinafter referred to as xe2x80x9caluminaxe2x80x9d) is deposited with a thickness of about 5.0 xcexcm to 10.0 xcexcm on a substrate 101 made of for example, altic (A2O3xe2x80x94TiC). Then, a bottom shield layer 103 for a reproducing head is formed on the insulating layer 102. Then, an alumina layer, for example, is deposited with a thickness of 100 nm to 200 nm on the bottom shield layer 103 by means of sputtering, and thus a shield gap film 104 is formed. Then, an MR film 105 for constituting an MR element for reproducing is formed into a desired pattern with a thickness of a few tens of nanometers on the shield gap film 104 by means of high-accuracy photolithography. Then, lead layers (not shown) for functioning as lead electrode layers to be electrically connected to the MR film 105 are formed on both sides of the MR film 105. After that, a shield gap film 106 is formed on the lead layers, the shield gap film 104 and the MR film 105, and thus the MR film 105 is sandwiched in between the shield gap films 104 and 106. Then, a top shield-cum-bottom pole (hereinafter referred to as xe2x80x9ca bottom polexe2x80x9d) 107 made of a magnetic material for use in both reproducing and recording heads, e.g., a nickel-iron alloy (NiFe, hereinafter referred to as xe2x80x9cPermalloy trade name)xe2x80x9d), is formed on the shield gap film 106.
Next, as shown in FIG. 40, a write gap layer 108 made of an insulating material, e.g., alumina, is formed on the bottom pole 107. Then, a photoresist film 109 is formed into a predetermined pattern on the write gap layer 108 by means of high-accuracy photolithography. Then, a thin film coil 110 made of, for example, copper (Cu) for an inductive recording head is formed on the photoresist film 109 by means of electroplating. Then, a photoresist is formed into a predetermined pattern by means of high-accuracy photolithography so as to coat the photoresist film 109 and the thin film coil 110, and thereafter the photoresist is subjected to heat treatment at a temperature of 250 degrees, for example. By this heat treatment, a photoresist film 111 for providing insulation between windings of the thin film coil 110 is formed.
Next, as shown in FIG. 41, a part of the write gap layer 108, which is located rearward with respect to the thin film coil 110 (on the right side in FIG. 41), is partly etched in order to form a magnetic path, whereby an opening 108A is formed and thus a part of the bottom pole 107 is exposed. Then, a top yoke-cum-top pole (hereinafter referred to as xe2x80x9ca top polexe2x80x9d) 112 made of a magnetic material for the recording head, e.g., Permalloy, is formed by means of electroplating so as to coat an exposed surface of the bottom pole 107, the photoresist film 111 and the write gap layer 108. For example, the top pole 112 has a planar shape shown in FIG. 44 to be described later and includes a yoke portion 112A and a pole chip portion 112B. The top pole 112 is in contact with and magnetically coupled to the bottom pole 107 in the opening 108A. Then, the respective parts of the write gap layer 108 and the bottom pole 107, which are located in a peripheral region around the pole chip portion 112B, are selectively etched and removed by about 0.5 xcexcm by means of ion milling using the pole chip portion 112B of the top pole 112 as a mask (see FIG. 43). Then, an overcoat layer 118 made of, for example, alumina is formed so as to coat the top pole 112. Finally, a track surface of the recording head and the reproducing head, i.e., an air bearing surface 120, is formed through the steps of machining and polishing, and thus a thin film magnetic head is completed.
FIGS. 42 to 44 show a structure of the completed thin film magnetic head. FIG. 42 shows a cross section of the thin film magnetic head in a direction perpendicular to the air bearing surface 120. FIG. 43 shows an enlarged view of a cross section of a pole portion 500 in a direction parallel to the air bearing surface 120. FIG. 44 shows a planar structure of the thin film magnetic head. FIG. 41 corresponds to a cross section viewed in the direction of the arrows along the line XXXXIxe2x80x94XXXXI of FIG. 44. FIGS. 42 to 44 do not show the overcoat layer 113 and so forth. FIG. 44 shows the thin film coil 110 and the photoresist film 111 whose outermost ends alone are shown.
In FIGS. 42 and 44, xe2x80x9cTHxe2x80x9d indicates a throat height, and xe2x80x9cMRHxe2x80x9d indicates an MR height. The xe2x80x9cthroat height (TH)xe2x80x9d refers to one of factors that determine the performance of the recording head, and refers to a length between the position of an edge of an insulating layer (the photoresist film 111) for electrically isolating the thin film coil 110 from the other conductive portions, more specifically, an edge closest to the air bearing surface 120, that is, a throat height zero position (a TH0 position), and the position of the air bearing surface 120. An optimization of the throat height (TH is desired for an improvement in the performance of the recording head. The throat height (TH) is controlled by the amount of polishing of the air bearing surface 120. The xe2x80x9cMR height (MRH)xe2x80x9d refers to a length between the position of an edge of the MR film 105, more specifically, an edge furthest from the air bearing surface 120, that is, an MR height zero position (an MRH0 position), and the position of the air bearing surface 120. The MR height (MRH) is also controlled by the amount of polishing of the air bearing surface 120.
Factors that determine the performance of the thin film magnetic head include an apex angle (xcex8) shown in FIG. 42, as well as the throat height (TH), the MR height (MRH) and so on. The apex angle xcex8 refers to an average degree of inclination of an inclined surface of the photoresist film 111 close to the air bearing surface 120.
As shown in FIG. 43, a structure in which the respective parts of the write gap layer 108 and the bottom pole 107 are etched in self-alignment with the pole chip portion 112B of the top pole 112 is called a trim structure. The trim structure allows preventing an increase in an effective track width resulting from a spread of a magnetic flux generated during the writing of data on a narrow track. xe2x80x9cP2Wxe2x80x9d indicates a width of a portion (hereinafter referred to as xe2x80x9ca pole portion 500xe2x80x9d) having the trim structure, namely, a pole width (or xe2x80x9ca track widthxe2x80x9d). xe2x80x9cP2Lxe2x80x9d indicates a thickness of the pole chip portion 112B constituting a part of the pole portion 500, namely, a pole length. Lead layers 121 or functioning as lead electrode layers to be electrically connected to the MR film 105 are provided on both sides of the MR film 105. The lead layers 121 are not shown in FIGS. 39 to 42.
As shown in FIG. 44, the top pole 112 has the yoke portion 112A occupying most of the top pole 112, and the pole chip portion 112B having a substantially uniform width as the pole width P2W. An outer edge of the yoke portion 112A forms an angle a with a surface parallel to the air bearing surface 120 in a coupling portion between the yoke portion 112A and the pole chip portion 112B. An outer edge of the pole chip portion 112B forms an angle xcex2 with the surface parallel to the air bearing surface 120 in the above-mentioned coupling portion. FIG. 44 shows the case where xcex1 and xcex2 are, for example, about 45 degrees and about 90 degrees, respectively. As described above, the pole chip portion 112B is a portion for functioning as a mask for forming the pole portion 500 having the trim structure. As can be seen from FIGS. 42 and 44, the pole chip portion 112B lies on the flat write gap layer 108, and the yoke portion 112A lies on a coil portion (hereinafter referred to as xe2x80x9can apex portionxe2x80x9d), which is coated with the photoresist film 111 and rises like a hill.
Detailed structural features of the top pole are described in Unexamined Japanese Patent Application Publication No. Hei 8-249614, for example. The publication gives the description about the top pole having a structure in which a width of the top pole becomes gradually greater rearward with respect to the TH0 position (that is, away from the air bearing surface 120).
The pole width P2W of the pole portion 500 defines a write track width on the magnetic recording medium. To increase the recording density, it is necessary that the pole portion 600 be formed with high accuracy so as to make the pole width P2W minutely small. Too great a pole width P2W causes the occurrence of a phenomenon in which data is written on not only a predetermined write track region on the magnetic recording medium but also regions adjacent to the predetermined write track region, namely, a aide erase phenomenon, which makes it impossible to increase the recording density. In recent years in particular, the local minimization of the pole width P2W to about 0.3 xcexcm or less has been required in order to enable recording at a high surface recording density, that is, in order to form the recording head having the narrow track structure, and therefore an urgent necessity is to establish manufacturing technology associated with the local minimization of the pole width P2W.
Frame plating is used as a method of forming the top pole, as described in Unexamined Japanese Patent Application Publication No. Hei 7-262519, for example. The top pole 112 is formed by using frame plating in the following manner. First, a thin electrode film made of, for example, Permalloy is formed on the overall underlayer including the apex portion by means of sputtering, for instance. Then, the electrode film is coated with a photoresist so as to form a photoresist film, and thereafter the photoresist film is patterned by means of photolithography, whereby a frame pattern (an outer frame) for plating is formed. The frame pattern has an opening pattern corresponding to the planar shape of the top pole 112. Then, the top pole 112 made of, for example, Permalloy is formed in the opening pattern of the frame pattern by means of electroplating using the frame pattern as a mask and using as a seed layer the electrode film formed in the preceding step.
The apex portion is located higher than the other portions by 7 to 10 xcexcm or more, for example. The apex portion is coated with a photoresist of 3 xcexcm to 4 xcexcm in thickness. When a film thickness of the photoresist on the apex portion must be at least 3 xcexcm or more, a photoresist film having a thickness of, for example, 8 to 10 xcexcm or more is formed under the apex portion because the fluidic photoresist flows intensively to a lower place.
To realize a locally minimum pole width P2W, it is necessary to form a frame pattern having an opening pattern having a locally minimum width (e.g., 1.0 xcexcm or less) corresponding to the pole width P2W. That is, the opening pattern having a locally minimum width of 1.0 xcexcor less must be formed by the photoresist film having a thickness of 8 to 10 xcexcm or more. However, it is very difficult in manufacturing process to form the frame pattern having the opening pattern having the locally minimum width by using the photoresist film having such a great film thickness.
When the top pole 112 is formed on a region having an uneven structure comprising the apex portion and so on, there is, moreover, a problem that the accuracy in forming the top pole 112 deteriorates greatly for the following reason. That is, when the photoresist film formed on the region having the uneven structure is exposed to light in the step of forming the frame pattern for forming the top pole 112, the light is reflected obliquely or transversely from an inclined surface portion or the like of the underlayer (the electrode film). The reflected light causes an increase or a reduction in an exposed region in the photoresist film. Therefore, in the photoresist film, the width of the opening pattern having the locally minimum width corresponding to the pole chip portion 112B of the top pole 112 increases in a width direction.
The invention is designed to overcome the foregoing problems. It is an object of the invention to provide a thin film magnetic head capable of local minimization of a pole width with high accuracy, a method of manufacturing the same, and a method of forming a magnetic layer pattern, which is capable of forming a long, narrow magnetic layer pattern with high accuracy.
In a thin film magnetic head according to a first aspect of the invention including: a first magnetic layer and a second magnetic layer magnetically coupled to each other and having two magnetic poles facing each other with a gap layer in between near and in a recording-medium-facing surface to be faced with a recording medium; a thin film coil provided between the first and second magnetic layers; and an insulating layer for insulating the thin film coil from the first and second magnetic layers, the first magnetic layer includes a laminate of a first magnetic layer portion and a second magnetic layer portion, the first magnetic layer portion being located away from the gap layer and the second magnetic layer portion being located close to the gap layer, the second magnetic layer portion extends adjacent to the gap layer from the recording-medium-facing surface to a first position, while maintaining a uniform width for defining a write track width on the recording medium, and the first magnetic layer portion includes a uniform width portion and a widened portion, the uniform portion extending from the recording-medium-facing surface or its neighborhood to a second position located at or near the first position, while maintaining the same width as the uniform width of the second magnetic layer portion, and the widened portion extending from the second position to a third position, and having a width greater than that of the uniform width portion.
In the thin film magnetic head according to the first aspect of the invention, the first magnetic layer portion is located away from the gap layer, and the second magnetic layer portion is located close to the gap layer, and the first magnetic layer includes these two magnetic layer portions. The uniform width portion of the first magnetic layer portion and the second magnetic layer portion have the same uniform width and define the write track width on the recording medium.
In the thin film magnetic head according to the first aspect of the invention, an edge on the recording-medium-facing surface side of the uniform width portion of the first magnetic layer portion may fall on the recording-medium-facing surface or may falls on a position away from the recording-medium-facing surface.
In the thin film magnetic head according to the first aspect of the invention, it is preferable that a thickness of an end, close to the recording-medium-facing surface, of the uniform width portion of the first magnetic layer portion be less than a thickness of an end, far from the recording-medium-facing surface, of the uniform width portion.
In the thin film magnetic head according to the first aspect of the invention, a boundary surface between the first magnetic layer portion and the second magnetic layer portion may be a plane.
In the thin film magnetic head according to the first aspect of the invention, the insulating layer may be in contact with the second magnetic layer portion at the first position. In this case, a boundary surface between the second magnetic layer portion and the insulating layer may be a plane, and the boundary surface may be perpendicular to a direction in which the second magnetic layer portion extends.
In the thin film magnetic head according to the first aspect of the invention, the thin film coil may include a first thin film coil, most of the first thin film coil may be included in a space defined by a thickness of the second magnetic layer portion. In this case, it is preferable that the thickness of the second magnetic layer portion be larger than a thickness of the first thin film coil.
In the thin film magnetic head according to the first aspect of the invention, a recessed area may be provided on a surface of the second magnetic layer close to the first magnetic layer, and the first thin film coil may be located in the recessed area.
In the thin film magnetic head according to the first aspect of the invention, when the thin film coil further includes a second thin film coil electrically connected to the first thin film coil, most of the second thin film coil may be included in a space defined by a thickness of the uniform width portion of the first magnetic layer portion.
In the thin film magnetic head according to the first aspect of the invention, the third position may be located between the recording-medium-facing surface and the first thin film coil, and the first magnetic layer may further include a third magnetic layer portion partially overlapping and magnetically coupled to the first magnetic layer portion. In this case, it is preferable that a part of the insulating layer be located adjacent to the gap layer in an overlap area in which the first magnetic layer portion overlaps the third magnetic layer portion.
In the thin film magnetic head according to the first aspect of the invention, a magnetic material of the second magnetic layer portion may have a saturation magnetic flux density equal to or higher than that of a magnetic material of the first magnetic layer portion. In this case, it is preferable that the first magnetic layer portion be made of a magnetic material containing iron, nickel and cobalt and the second magnetic layer portion be made of a magnetic material containing either a nickel-iron alloy or a cobalt-iron alloy.
In the thin film magnetic head according to the first aspect of the invention, at least one of the first and second magnetic layer portions may be made of a magnetic material containing iron nitride, a nickel-iron alloy or an amorphous alloy. Preferably, the amorphous alloy is a cobalt-iron alloy, a zirconium-cobalt-iron alloy oxide or a zirconium-iron alloy nitride.
In the thin film magnetic head according to the first aspect of the invention, at least one of the first and second magnetic layer portions may be made of a magnetic material containing iron, nickel and cobalt.
In a thin film magnetic head according to a second aspect of the invention including: a first magnetic layer and a second magnetic layer magnetically coupled to each other and having two magnetic poles facing each other with a gap layer in between near and in a recording-medium-acing surface to be faced with a recording medium; a thin film coil provided between the first and second magnetic layers; and an insulating layer for insulating the thin film coil from the fist and second magnetic layers, the it magnetic layer includes a track width defining portion extending adjacent to the gap layer away from the recording-medium-facing surface and defining a write track width on the recording medium, and the track width defining portion has a multilayer structure comprising a plurality of magnetic layers.
In the thin film magnetic head according to the second aspect of the invention, the track width defining portion is adapted to have the multilayer structure comprising a plurality of magnetic layers, and the track width defining portion defines the write track width on the recording medium.
In a method of manufacturing a thin film magnetic head according to a first aspect of the invention including: a first magnetic layer and a second magnetic layer magnetically coupled to each other and having two magnetic poles facing each other with a gap layer in between near and in a recording-medium-facing surface to be faced with a recording medium; a thin film coil provided between the first and second magnetic layers; and an insulating layer for insulating the thin film coil from the first and second magnetic layers, the first magnetic layer including a laminate of a first magnetic layer portion and a second magnetic layer portion, the first magnetic layer portion being located away from the gap layer and the second magnetic layer portion being located close to the gap layer, the second magnetic layer portion extending adjacent to the gap layer from the recording-medium-facing surface to a first position while maintaining a uniform width for defining a write track width on the recording medium, the first magnetic layer portion including a uniform width portion and a widened portion, the uniform width portion extending from the recording-medium-facing surface or its neighborhood to a second position located at or near the first position, while maintaining the same width as the uniform width of the second magnetic layer portion, and the widened portion extending from the second position to a third position and having a width greater than that of the uniform width portion, the step of forming the first magnetic layer includes: a first step of selectively forming a precursory magnetic layer having a width greater than the uniform width of the second magnetic layer portion and a straight edge extending in a width direction of the second magnetic layer portion at the first position and functioning as a preparatory layer for the second magnetic layer portion, on the gap layer in a region from a position nearby which the recording-medium-facing surface is to be formed to the first position; a second step of forming a precursory insulating layer covering at least the precursory magnetic layer and a periphery thereof and functioning as a preparatory layer for a part of the insulating layer; a third step of polishing and flattening the precursory insulating layer until at least the precursory magnetic layer is exposed, thereby forming the part of the insulating layer; a fourth step of selectively forming the first magnetic layer portion on a polished and flattened surface so that the second position of the uniform width portion is located further from the recording-medium-facing surface than the first position; and a fifth step of selectively etching the precursory magnetic layer with the uniform width portion of the first magnetic layer portion as a mask, thereby forming the second magnetic layer portion.
In the method of manufacturing a thin film magnetic head according to the first aspect of the invention, the first step includes selectively forming a precursory magnetic layer having a width greater than the uniform width of the second magnetic layer portion and a straight edge extending in a width direction of the second magnetic layer portion at the first position, and functioning as a preparatory layer for the second magnetic layer portion, on the gap layer in a region from a position nearby which the recording-medium-facing surface is to be formed to the first position. Then, the second step includes forming a precursory insulating layer covering at least the precursory magnetic layer and a periphery thereof and functioning as a preparatory layer for a part of the insulating layer. Then, the third step includes polishing and flattening the precursory insulating layer until at least the precursory magnetic layer is exposed, thereby forming the part of the insulating layer. Then, the fourth step includes selectively forming the first magnetic layer portion on a polished and flattened surface so that the second position of the uniform width portion is located farther from the recording-medium-facing surface than the first position. Finally, the fifth step includes selectively etching the precursory magnetic layer with the uniform width portion of the first magnetic layer portion as a mask, thereby forming the second magnetic layer portion, and thus the first magnetic layer is formed through the above-mentioned steps.
In the method of manufacturing a thin film magnetic head according to the fist aspect of the invention, it is preferable that the fifth step include using reactive ion etching to form the second magnetic layer portion.
In the method of manufacturing a thin film magnetic head according to the first aspect of the invention, it is preferable that the first step include using reactive ion etching to form the precursory magnetic layer.
In the method of manufacturing a thin film magnetic head according to the first aspect of the invention, the fifth step may include removing the gap layer and the second magnetic layer to a predetermined depth in a thickness direction, except for a region where the uniform width portion of the first magnetic layer portion is formed.
In the method of manufacturing a thin film magnetic head according to the first aspect of the invention, it is preferable that the precursory magnetic layer be formed by steps of depositing a magnetic material layer on the gap layer with sputtering and selectively etching the magnetic material layer, and the first magnetic layer portion be formed with plating.
In a method of manufacturing a thin film magnetic head according to a second aspect of the invention including: a first magnetic layer and a second magnetic layer magnetically coupled to each other and having two magnetic poles facing each other with a gap layer in between near and in a recording-medium-facing surface to be faced with a recording medium; a thin film coil provided between the first and second magnetic layers; and an insulating layer for insulating the thin film coil from the first and second magnetic layers, a step of forming the first magnetic layer includes a step of forming a laminate including a first magnetic layer portion, the first magnetic layer portion being located away from the gap layer and the second magnetic layer portion being located close to the gap layer, the second magnetic layer portion is formed so as to extend adjacent to the cap layer from the recording-medium-facing surface to a first position with a uniform width for defining a write track width on the recording medium, and the first magnetic layer portion is formed so as to include a uniform width portion and a widened portion, the uniform width portion from the recording-medium-facing surface or its neighborhood to a second position located at or near the first position, while maintaining the same width as the uniform width of the second magnetic layer portion, the widened portion extending from the second position to a third position, and having a width greater than the width of the uniform width portion.
In the method of manufacturing a thin film magnetic head according to the second aspect of the invention, the first magnetic layer is formed by forming a laminate of a first magnetic layer portion and a second magnetic layer portion, the first magnetic layer portion is located away from the gap layer and the second magnetic layer portion is located dose to the gap layer. The step of forming the second magnetic layer portion includes forming the second magnetic layer portion which extends adjacent to the gap layer from the recording-medium-facing surface to a first position, while maintaining a uniform width for defining a write track width on the recording medium. The step of forming the first magnetic layer portion includes forming a uniform width portion and widened portion, for constituting parts of the first magnetic layer portion, the uniform portion extending from the recording-medium-facing surface or it neighborhood to a second position located at or near the first position, while maintaining the same width as the uniform width of the second magnetic layer portion, and the widened portion extending from the second position to a third position and having a width greater than that of the uniform width portion, thereby forming the first magnetic layer portion including the uniform width portion and the widened portion.
In the method of manufacturing a thin film magnetic head according to the second aspect of the invention, when the thin film coil includes a first thin film coil the first thin film coil may be formed so that most of the first thin film coil is included in a space defined by a thinness of the second magnetic layer portion. In this case, a recessed area may be formed on a surface of the second magnetic layer dose to the first magnetic layer by etching a part of the second magnetic layer to a predetermined depth, and the first thin film coil may be formed in the recessed area.
In the method of manufacturing a thin film magnetic head according to the second aspect of the invention, when the thin film coil further includes a second thin film coil electrically connected to the first thin film coil, the second thin film coil may be formed so that most of the second thin film coil is included in a space defined by a thickness of the first magnetic layer portion.
A method of forming a magnetic layer pattern of the invention, for forming a slim magnetic layer pattern extending with a uniform width on a predetermined underlayer, includes the steps of: selectively forming, on the underlayer, a precursory magnetic layer having a width greater than the uniform width of the magnetic layer pattern and a straight edge extending in a width direction of the magnetic layer pattern and functioning as a preparatory layer for the magnetic layer pattern; forming a nonmagnetic layer covering at least the precursory magnetic layer and a periphery thereof polishing and flattening the nonmagnetic layer until at least the precursory magnetic layer is exposed; selectively forming, on a polished and flattened surface, an etching mask which crosses the straight edge of the precursory magnetic layer, extends from a surface region of the nonmagnetic layer to a surface region of the precursory magnetic layer and has the same width as the uniform width of the magnetic layer pattern to be formed; and selectively etching the precursory magnetic layer with the etching mask, thereby forming the magnetic layer pattern.
In the method of forming a magnetic layer pattern of the invention, first, a precursory magnetic layer which has a width greater than the uniform width of the magnetic layer pattern and a straight edge extending in a width direction of the magnetic layer pattern and functions as a preparatory layer for the magnetic layer pattern is selectively formed on the underlayer. Then, a nonmagnetic covering at least the precursory magnetic layer and a periphery thereof is formed. Then, the nonmagnetic layer is polished and flattened until at least the precursory magnetic layer is exposed. Then, an etching mask, which crosses the straight edge of the precursory magnetic layer, extends from a surface region of the nonmagnetic layer to a surface region of the precursory magnetic layer and has the same width as the uniform width of the magnetic layer pattern to be formed, is selectively formed on a polished and flattened surface. Finally, the precursory magnetic layer is selectively etched with the etching mask, thereby the magnetic layer pattern is formed.
Other and further objects, features and advantages of the invention will appear more fully from the following description.